This invention relates to a refueling check valve assembly, and more particularly to such a valve assembly having a manual by-pass feature for use in compressed natural gas (CNG) powered vehicles.
Because of environmental concerns and emissions laws and regulations, manufacturers of motor vehicles are searching for a clean burning and cost efficient fuel to use as an alternative to gasoline. Natural gas is one candidate for such a purpose, and many vehicles have been converted to natural gas as a fuel source. Typically, the natural gas is stored on board the vehicle in compressed form in one or more pressurized cylinders. After the fuel is expended, there is a need to be able to refill the cylinders under pressure in a safe, fast, and efficient manner.
Refueling valves which control the supply of compressed natural gas (CNG) to the cylinders in a vehicle are exposed to large variations in environmental conditions. For example, wide variations in temperatures and pressures may be encountered. During refueling operations, instantaneous temperature drops of at least 50.degree. F. are common. Temperatures may exceed ambient by 20.degree. F. or more toward the end of refueling. This variation in temperature, as well as the rapid increases in pressure during refueling, may result in the nominal working pressure in a gas cylinder varying from several hundred up to several thousand pounds per square inch (psi). Thus, the refueling valve must be able to handle high gas pressures up to 4,500 psi without leakage or failure.
Additionally, nozzles transferring the compressed natural gas fuel through the refueling valves under these high pressures must be able to be fully depressurized prior to being disconnected from the refueling valves. Also, in view of the long lives of the vehicles and the potential for many thousands of refuelings over the life of a vehicle, the refueling valves must be able to withstand many thousands of refueling cycles. Finally, if servicing or replacement of a valve is necessary, the system must be able to be vented and depressurized readily.
Currently, refueling valves are designed with a receptacle adapted to mate with a fueling nozzle and have a check valve positioned within the receptacle. Such designs, however, may be difficult to service or replace. Accordingly, the need exists in this art for a refueling valve which provides for easy and safe refueling and yet is convenient to service or replace.